US1708996A - Mercury switch - Google Patents

Description

April 16,- 1929. W, R ARMSRONG 1,708,996

MERCURY SWITCH Filed April 6, 1928 Patented Apr.'` 16, 1929.,

WALTER R. ARMSTRONG, OF CHICAGO,

ILLINOIS, ASSIG-NOR OF ONE-HALF TO FRANKLIN MAYO, OF CHICAGO, ILLINOIS.

MERCURY SWITCH.

Application filed April 6, 1928.

My invention relates to mercury Switches of the kind wherein a quantity of mercury within ra tilting tube acts to establish and break a circuit having its conductors terminating in the tube.

Tilting mercury switches which have been known and used for many years have been of two general types, namely those wherein opening and closing of a circuit is effected by the separation and coming together of portions of a body of mercury, and those wherein the mercury does not separate but, in its movements, engages and disengages with one f a pair of fixed electrodes to establish and break a conducting path between a pair of such electrodes.

All of these mercury switches with which we have heretofore been familiar have been subject to certain serious objections when utilized to interrupt the flow of currents of any considerable ampere strength,-objec tions which have come to be regarded as inherent and unavoidable in this kind of switch.

The impingement of recurring arcs upon the glass or other material ofthe tube detaches small particles of the tube material at or adjacent the point wherein the arcing occurs and eventually causes disruption of the tube. Moreover, the co-mingling of the detached particles of the tube material with the mercury tends to make the action of the latter more sluggish than is desirable. Fitting of the tube by arcing also oftentimes impairs .the performance of the mercury. Furthermore,

the continuous occurrence of substantial arcs in the mercury switch has an objectionable effect upon the mercury, making its flow sluggish and causing the mercury and /or impurities therein contained to give off gases which cloud the tube, which preferably should be transparent.

The disadvantages just mentioned are practic-ally eliminated by the present invention, two characteristic embodiments of which are illustrated in the accompanying drawing.

In the drawing: l.

Figure l is a longitudinal section of a switch tube and its associated parts constructed and arranged in accordance with my presling and tilting mechanism being omitted, and the circuit connections being diagrammatically illustrated; and

Figure 2 is a similar view illustrating a modified embodiment of the invention, where- `ent invention,-the conventional tube hold-- Serial No. 267,857.

in the reduction and interruption of the eurrent flow is effected by the actual disengagement of the mercury from fixed electrodes, as distinguished from the arrangement of Figure 1, wherein the reduction and interruption of the current flow is accomplished by separation of the mercury into disconnected portions.

Referring to the drawings, the switch tube, preferably formed of glass, is illustrated at 3, this tube containing a quantity of mercury 4l and also preferably containing one of the gases found suitable for use in these tilting mercury switches, for instance, hydrogen. Ordinarily, as is well understood in the art, these tubes are supported upon a tilting mechanism (not shown), whichv in turn is acted upon by a suitable controlling or operating mechanism to tilt the tube when the circuit controlled by the switch is to be completed or broken. For the purposes of the present description, it may be assumed that the tube moves in a vertical plane around the axis or fulcrum F, tion of the feathered arrow A when the circuit is to be opened, and being tilted in the being tilted in the diree.

direction of the unfeathered arrow B when the circuit is to be closed.

The tube shown in Figure 1 is provided with three depressions or wells 5, 6 and 7 a certain portion of the mercury always remaining in each of these wells. Ordinarily, the tube 3 will be tilted in the direction of the feathered arrow A sufliciently to vcause the main body of mercury 4 successively to separate itself from the mercury contained in the wells 5 and 6, but not necessarily sufficiently to cause a separation of the main body of mercury from the portion contained in the well 7. Thus, for the purpose of the specifi cation and the appended claims, mercury portions which always remain in the wells 5 and 6 may be regarded as mercury electrodes from which the main body of mercury 4 is detached and with which the said main body of mercury is caused to hereinafter explained.

The wells', 6 and 7 are conveniently located in bosses or enlarged portions of the tube wall, as illustrated. Entering each of these enlarged portions is a lead in wire 8. conveniently of copper, the' inner end of which is connected in the usual manner with a suitable metal alloy 9, which is imbedded in the glass and has substantially the same join for the purposes coefficient of expansion as the glass. From each of the elements 9 extends a short conductor 10, which is at all times in electrical contact with the mercury portion contained in the well into which it projects. rl`he conductors 10 are preferably formed of iron or other material which will not become amalgamated with mercury. lVhenever the conductors 10 are not formed of iron, the portions thereof, which otherwise would be eX- posed to Contact with the mercury, may be protected by small sleeves 1l of iron, carbon or the like. The sleeves 11 also serve the purpose otl increasing the surface contact between the mercury and the conductors projertiug into the wells.

At C and C are indicatedl the conductors of a circuit controlled by my improved switch, the conductor C being at all times connected with the mercury electrode 8, and the conductor C being at all times connected with the mercury electrode 5. Mercury electrode G is at all times connected through a relatively high resistance 12 with the mercury electrode 5.

It will be understood without illustration that the conductors connecting with the lead in wires 8 will be sufficiently flexible to per- -mit ready tilt-ing of the tube, and that the resistance winding 12 will preefrably, .but not necessarily, be mounted at some convenient point upon the tube holding and tilting mechanism.

With the tube in the position shown in Figure 1, the circuit controlled by the switch will be closed without encountering any appreciable resistance in the switch. Upon tilting of the tube in the direction of the arrow A, the main body of mercury will move toward the lower end of the tube, the first result of this movement being a physical separation of the main body of mercury from that which always occupies the well 5. This separation of the mercury electrode in the well 5 from the vmain body of mercury is not accompanied by any arc, or any substantial arc, due to the continuance of current How through the high resistance path, including the resistance 12. Ordinarily the coil or winding 12 will have such resistance as to reduce the current .iiow by eighty or ninety percent immediately following the interruption of the low resist-ance path through the switch. Almost immediately following the interruption of the low resistance path, the high resistance path, including the winding 12, will be interrupted by the separation of the main body of mercury from the mercury always occupying the well 6, but in this instance there will be vno are, or any appreciable arc, due to the fact that the current now flowing is an extremely small part of the normal current flow. The circuit controlled by the switch is now opened. On reverse tilting of the tube, in the direction of the arrow B, the circuit controlled by the switch is lirst closed through the resistance winding 12, and is then almost immediately given a low resistance path around the resistance 12, when the main body of mercury joins the mercury contained in the well 5.

rI`he embodiment of my invention illustrated in Figure 2 requires no particular comment, except perhaps to say that in this instance the electrodes 5, G and 7 are fixed electrodes, preferably of iron, with which the mercury 4 makes and breaks contact when the tube is tilted to and fro.

Either of the constructions illustrated in the accompanying drawings will eliminate and/or minimize all of the hereinbefore mentioned objections of the two electrode mercury switches of the prior art. I believe I am the first to suggest providing a tilting mercury switch with a multiplicity of electrodes and/or a resistance for the purposes herein set forth.

- I-Iaving thus described two practical embodiments of my invention, I do not limit myself to the particular constructions here in set forth, but wish to cover all the equivalent constructions falling wit-hin the terms and spirit of the appended claims.

What I claim as new and desire to secure by Letters Patent of the United States, is:

1. A mercury switch comprising a tube tiltable about a fulorum, a quantity of mercury in said tube, three spaced electrodes extending into said tube through one end thereof and terminating at different distances from the fulcrum of said tube, the said electrodes valso being spaced from each other so that contact with the mercury is made and broken serially.

2. A mercury switch comprising a tube tiltable about a fulcrum, three spaced electrodes extending into said tube through one end thereof and terminating in downturned ends spaced from each other and at different distances from the fulcrum of the tube whereby contact will be made and broken serially.

In witness whereof, I hereunto subscribe my name this 3rd day of April, 1928.

WALTER R. ARMSTRONG.

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